My wife’s 2011 Volkswagen Jetta (2.0 I believe) is misfiring again. We took it to the dealership about 6 months ago and they said that the ignition coil had gone bad. They replace the ignition coil and said that the plugs needed changing as well. I went to Auto Zone and got some decent plugs and changed them myself at home without much problem. It seemed to help the problem (although it didn’t seem to completely fix it) for a while, but it just recently went back to misfiring. The current symptom is that it seems to misfire when the car is warming up, but misfires less when the car is warm.

The dealership says that the plugs that we got were not recommended by the dealer (they recommended Bosch) and that they need to be replaced. I think this is BS and it is not going to fix the problem. Could the ignition wires be the problem? Any other suggestions?

Yes, the ignition wires could be the problem, but it is also very possible that the spark plugs are the problem.

Even if you think that the dealer’s comment is BS, the reality is that modern ignition systems are very “touchy” when it comes to the spark plugs that are used. If the mfr specifies the incredibly expensive iridium plugs, that is what you need to use if you want to avoid problems. Ditto with platinum plugs. “Regular” copper-core spark plugs cannot properly replace the other, more-expensive plugs.

Even the brand/model of spark plugs can be problematic, and cheaping-out on spark plugs is a very good example of being penny-wise and dollar-foolish. If you want to avoid problems, you should use only the exact same type/brand/model spark plugs that are specified in your Owner’s Manual.

Wow! I had no idea that plugs (even though these were not necessarily the cheap ones) would be the problem. That could explain why it solved the problem for a little while and then it got worse again. Thanks for the fast reply. Seems like you could go 100,000 miles on a pair of plugs back in the day. I guess modern cars eat up plugs now.

" Seems like you could go 100,000 miles on a pair of plugs back in the day. I guess modern cars eat up plugs now."

No, you’re missing the point. Modern plugs (platinum, iridium, etc) do last much longer than “back in the day” plugs.

But installing the incorrect TYPE or even brand of plug as you did can quickly cause ignition problems or even damage a coil, which as VDC said are much more sensitive to spark plug characteristics than “back in the day” ignition systems.

So a more correct statement is: “Modern car ignition systems can get eaten up quickly by incorrect spark plugs.”

Golly, am I ever going to hear of a Jetta without problems? You’d think Germans, of all people, would get their cars right pre-delivery. I don’t get it. Iridium plugs are great, BUT, plugs won’t fix internal troubles. My solution - trade it in for a Kia or Hyundai or Chevy Impala (ones w/out CVTs, of course). And, a coil going bad after 3 years?!!! That’s inexcusable. One thing I’ll agree with the dealer on, BOSCH plugs (and ignition wires) are the BEST. Bosch got the original patent on spark plugs way back @ 1900. I put Bosch Iridium plugs and Bosch ignition wires in my American car (gosh I hope I’m not being unpatriotic by buying American) about 7 months ago and the difference in performance is incredible - I am very happy with Bosch. Sounds like you may have a vacuum leak or a failed gasket.